Element attachable by riveting to a sheet metal part and also a component assembly and a method for the production of the component assembly

ABSTRACT

An element attachable to a sheet metal part by riveting, in particular an element in the form of a centering bolt, having a shaft part and a head part, wherein the head part has at its side confronting the sheet metal part an at least approximately ring-like ring recess which merges at the radially inner side into a cylinder section of the head part which in turn merges into the shaft part and into a tubular rivet section which surrounds the shaft part in the region of the head part, is disposed within a ring-like contact surface arranged radially outside of the ring recess and merges at the radially outer side via an at least approximately conical wall into the ring-like contact surface, is characterized in that at least one local recess and preferably a plurality of in particular uniformly distributed local recesses is or are provided in the conical wall of the ring recess and/or in an optionally present ring-like base surface of the ring recess. A component assembly comprising the element and a sheet metal part and also a method for the manufacture of such a component assembly are also described.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of Ser. No. 11/303,766, filed Dec. 16,2005, pending, which claims priority of German Patent Application No. 102004 062 391.0 filed Dec. 23, 2004, the contents of all of which areincorporated herein in their entirety by reference.

FIELD OF THE INVENTION

The present invention relates to an element attachable to a sheet metalpart by riveting, in particular an element in the form of a centeringbolt, having a shaft part and a head part, wherein the head part has atits side confronting the sheet metal part an at least approximatelyring-like ring recess, which merges at the radially inner side into acylinder section of the head part which in turn merges into the shaftpart and into a tubular rivet section which surrounds the shaft part inthe region of the head part, is disposed within a ring-like contactsurface arranged radially outside of the ring recess and merges at theradially outer side via an at least approximately conical wall into thering-like contact surface. Furthermore, the invention relates to acomponent assembly comprising a sheet metal part to which the element isattached and also a method for the attachment of the element to a sheetmetal part.

An element, a component assembly and also a method of the initiallynamed kind are known from FIGS. 8 and 9 of EP-A-0 539 793. In the methoddescribed there the sheet metal part is so designed that it has aconical raised portion in the region of the attachment, with the shaftpart of the bolt provided with the thread and also the ring-like rivetsection being introduced through a central opening of the conical raisedportion coming from the raised side, with the upper, region of theconical raised portion being pressed flat during the riveting processand with the rivet bead coming to lie within a ring recess at theunderside of the sheet metal part, i.e. at the side of the sheet metalpart remote from the head part of the bolt element, with the ring recessstill being present even after the partial pressing flat of the conicalraised portion.

In the illustrated embodiment a plurality of noses providing securityagainst rotation are pre-sent which are distributed uniformly in theperipheral direction, which are present in the region of the transitionof the ring recess of the head part into the ring-like rivet section andwhich have a triangular shape in side view, with the noses providingsecurity against rotation extending in the radial zone only over a partof the width of the ring recess.

Bolt elements of this kind have, however, not been used in practice. Onereason for this is that the noses providing security against rotation onthe one hand tend, if anything, to hinder the desired reshaping of asheet metal part and, on the other hand, stiffen the ring-like rivetsection whereby the beading over of the beading section provesdifficult. Furthermore a design of this kind can lead to undesireddeformations of the sheet metal. In this type of element the die buttonwhich is responsible for the formation of the rivet bead and for there-shaping of the sheet metal part presses against the rivet bead andthe rivet bead presses against the sheet metal part. Accordingly therivet bead which is being formed has to press the sheet metal partagainst the noses providing security against rotation and press thenoses providing security against rotation into the sheet material. Thisproves difficult in practice and it can transpire that the sheetmaterial is caught up at the noses providing security against rotationwhereby the formation of the rivet bead fails and the rivet section isdeformed and centrally pressed quasi radially into the sheet material.

A series of applications are known in technology in which an elementattached to a sheet metal part by riveting is to serve as a centeringelement. In this connection the element has a part zone of the shaftwhich fits relatively tightly within a hole of a further component whichis attached to the element riveted to the sheet metal part and which isto be accurately positioned relative to the sheet metal part. In thisconnection the centering element can have a purely centering function,with the screwing on of the further component to the sheet metal partbeing effected by other elements, or the centering element cansimultaneously be provided with a thread which serves for the attachmentof the further component to the sheet metal part. The element then hasnot only a centering function but also an attachment function.

Such centering elements or centering and fastener elements have hithertobeen realized by the component Profil Verbindungstechnik GmbH & Co. KGin the form of so-called SBF bolts which are for example described inGerman patent 3447006.9. In an SBF bolt element the end of the head partremote from the shaft part is designed for a rivet connection with thesheet metal part.

Although such centering elements, optionally with a fastening function,have proved them-selves in practice, the attachment to the sheet metalpart in the region of the head part of the element requires a relativelylarge re-shaping of the sheet metal part and of the head part. Thisleads to a situation in which, for elements with a shaft diameter of 12mm or more, relatively large reshaping forces are required in order toachieve the required rivet connection to the sheet metal part. This isin particular problematic when the sheet metal part has a considerablethickness which is frequently the case when using centering elementswith a larger shaft diameter.

A similar problem arises also with other fastener elements which can beused for centering purposes.

A further element which can be used as a centering element is describedin WO 02/077468. This is a functional element with a head part having aring-like contact surface and a tubular rivet section standing away fromthe head part at the side of the contact surface of the head part, witha tubular guide section being disposed concentrically to the tubularrivet section and radially within the latter, with a ring gap beingprovided between the guide section and the rivet section and with theguide section projecting beyond the free end of the rivet section.

The free end of the wall of the tubular rivet section is rounded both atthe radially outer side and also at the radially inner side when seen inan axial section plan and has for example a semicircular shape or ashape resembling an arrow tip which is helpful for the formation of therivet bead. The guide section is formed as a piercing section and has,at its end remote from the contact surface, a ring-like cutting edge sothat the element can be introduced in self piercing form into a sheetmetal part. The element is formed as a nut element which first makes theself-piercing function possible. In this element no ring recess ishowever provided in the ring-like contact surface and the nosesproviding security against rotation have the shape of raised portions orribs which extend in the radial direction and which are formed at thering-like contact surface.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an element of theinitially named kind which can have a purely centering function as wellas a centering and attachment function, with forces being required forthe attachment to the sheet metal part which remain within accept-ablelimits even with shaft diameters of 12 mm and larger, with undesireddeformation of the sheet metal part not having to be feared and with itbeing possible to use only one element with sheet metal parts of variousthicknesses with an excellent resistance to rotation being achieved.

In order to satisfy this object an element of the initially named kindis provided which is characterized in that at least one local recess andPreferably a plurality of in particular uniformly distributed localrecesses is or are provided in the conical wall of the ring recessand/or in an optionally present ring-like base surface of the ringrecess.

Through the provision of features providing security against rotation inthe form of a local recess or of a plurality of uniformly distributedrecesses in the conical wall of the ring recess and/or in a tubular basesurface of the ring recess a situation is prevented, in particular withthicker metal sheets, that the features providing security againstrotation represent a resistance during the attachment of the element tothe sheet metal part which has first to be overcome for the shaping ofthe sheet metal part or for the reshaping of the rivet section.Furthermore, such recesses providing security against rotation lead to asituation in which no undesired deformation of the sheet metal partarises which is of particular significance for a centering element.Moreover, such recesses providing security against rotation ensure anadequate rotational security and do not prevent the rivet bead beingformed such that it can be fully received within a ring recess presentat the lower side of the sheet metal part, i.e. at the side of the sheetmetal part remote from the head part of the element, so that a flatattachment surface is present at the lower side of the sheet metal part.This in turn gives the guarantee that the guide section of the elementwhich brings about the centering can also be provided directly at theunderside of the sheet metal part, i.e. at the free end face of therivet bead which is present at the shaft part of the element so that anideal centering or positioning of a component is ensured which isdisposed over the guide section of the element.

Furthermore, the element in accordance with the invention can be used inone embodiment with different sheet metal thicknesses in a relativelywide range. For example only two different elements are required tocover a range of sheet metal thicknesses from for example 0.6 to beyond3.5 mm without the rivet bead which is positioned in the ring recess atthe lower side of the sheet metal part projecting beyond the lower sideof the sheet metal part and causing in difficulties during theattachment of the further component. For example, in a first embodimentwith a short rivet section, sheet metal thickness of 0.6 to 1.5 mm canbe covered while a second embodiment with a longer rivet section can beused for sheet metal thicknesses from for example 1.5 to over 3.5 mm. Inparticular one succeeds in using one element with a somewhat shorterrivet section for sheet metal thicknesses in the range 1.25 to over 3.0mm and this represents a range which very frequently arises forcentering bolts. It should also be stated that the invention is in noway restricted to elements with a shaft diameter of approximately 12 mm,but rather the shaft diameter used can be selected in a broad range, forexample—without restriction—in the range from 4 mm to 38 mm.

The element in accordance with the invention also has the advantage thatit is possible to carry out the so-called clamping hole riveting processin accordance with the European patent 0 539 793 B1 and to herebyachieve the desired stranglehold between the sheet metal part and theelement. In other words the (partial) pressing flat of the conicalraised portion can be exploited in order to reduce size of the centralopening of a sheet metal part during the carrying out of the rivetingprocess, so that the rim region of the opening enters into contact withthe sheet metal of the element in the region above the rivet section orin the region of the rivet section while the latter is turned overradially outwardly through the riveting process and optionally radiallyexpanded by the riveting process.

It is, however, not essential to use the clamping hole riveting processbut rather the shape of the conical raised portion can be matched to theshape of the ring recess in the underside of the head part of theelement since, during the beading over of the rivet section, the diebutton can so crush the sheet metal material between itself and the headpart of the element that the sheet metal material not only flows intothe local recess or recesses but rather also is urged radially inwardly,where by the stranglehold which is aimed at can likewise be achieved.

Even when the fastener element has a pure centering function it isfavorable to provide the features providing security against rotationinto the form of the local recess or recesses, since one can in this wayprovide a simple possibility of ensuring that the method for theattachment of the element to a sheet metal part takes place with therequired process reliability. One can namely, after attachment of theelement of the sheet metal part and with appropriate support of thesheet metal part apply torques to the element in an attempt to twist theelement out of the sheet metal part or to loosen it in the sheet metalpart. The level of the torque which arises is a measure as to how firmlythe element is attached to the sheet metal part and can be used toensure quality or to check quality.

With an element having a fastening function the features providingsecurity against rotation are in any event necessary in order to ensurethat the attachment function can be achieved, i.e. to produce therequired security against rotation during the attachment of a nut to theshaft part of an element realizes a bolt element or during the screwingof a screw into a hollow shaft part of an element formed as a nutelement. When forming the element as a nut element the thread can beprovided in the head part, in the hollow shaft part and/or in anattachment section which is provided at the side of the head part remotefrom the shaft part. In the latter case the attachment sectionpreferably has a smaller outer diameter than the head part of theelement, whereby a ring-like contact pressure surface can be providedwhich enables the pressing of the element into the sheet metal part andthe carrying out of the riveting process without the fastener sectionbeing deformed by the forces which arise. In the event of realization ofthe element as a nut element it could also be made self-piercing.

The component assembly in accordance with the invention is characterizedin that the sheet metal part has a ring-like raised formation in theregion of the ring recess which is received in the ring recess; in thatmaterial of the sheet metal part is disposed in the or in each localrecess and in that the sheet metal part has, at the side remote from thering recess, a ring recess into which the rivet section which has beenturned over into a rivet bead is disposed, with the side of the rivetbead remote from the head part at least substantially not projectingbeyond the side of the sheet metal part in the region around the rivetbead and preferably being set back slightly relative to the latter.

Finally, the method of the invention for the attachment of an element toa sheet metal part for the formation of a component assembly ischaracterized in that the element is inserted into a pre-holed sheetmetal part which is preferably pre-shaped in the region of the hole toform a raised portion which is matched at least substantially to theshape of the ring recess or preferably has a steeper conical shape thanthe conical wall; in that the sheet metal material around the rivetsection is formed by means of a die button having a central recess or acentral bore which receives the shaft part and a ring-like raisedportion which surrounds the central section or the bore, into the oreach local recess and the rivet section is laid or pressed into the ringrecess formed in the underside of the sheet metal part during formationof the rivet bead.

In this embodiment the ring-like raised portion of the die button isformed at its free end at least substantially with a ring edge whichmerges into a rounded shaping surface disposed radially outside of thering edge, whereby the rivet section is re-shaped into a rivet bead. Inthis connection the ring edge has a diameter which is smaller than thatof the tubular rivet section in the region of the ring apex of the freeend of the rivet section, so that the ring edge can deflect the rivetbead radially outwardly during the riveting process.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The invention will be explained in more detail in the following withreference to the drawings in which:

FIGS. 1A-C show three views of an element in accordance with theinvention with a pure centering function, with FIG. 1A showing theelement in a perspective illustration at the underside of the head part,FIG. 1B being an illustration of the element in FIG. 1A sectioned partlyin longitudinal direction, and FIG. 1C showing a plan view of theunderside of the head part of the element in accordance with FIGS. 1Aand 1B,

FIGS. 2A-B show the attachment of the element of the invention inaccordance with FIGS. 1A-1C to a sheet metal part, with FIG. 2A showingthe state prior to the introduction of the element through the centralopening of a conical raised portion and FIG. 2B showing the componentassembly in a partly sectioned representation,

FIGS. 3A-C correspond to FIGS. 1A-1C but show a modified embodiment inthe form of a centering element with a fastening function,

FIGS. 4A-B correspond to FIGS. 2A-2B but show the attachment of the boltelement of FIGS. 3A-3C to a sheet metal part,

FIG. 5 shows the screw-on situation in which a component is attached tothe component assembly which is shown in FIG. 4B,

FIGS. 6A-C show three views of a further embodiment of an element inaccordance with the invention, with FIG. 6A showing the element in aperspective illustration at the underside of the head part, FIG. 6Bbeing an illustration of the element in FIG. 6A sectioned partly inlongitudinal direction, and FIG. 6C showing a plan view of the undersideof the head part of the element in accordance with FIGS. 6A and 6B, and

FIG. 7A-D show further embodiments of elements attached to a component.

DETAILED DESCRIPTION

Referring to FIGS. 1A to 1C and FIGS. 2A to 2B an element 12 is shownwhich is attached to a sheet metal part 10 by riveting. The element 12has the form of a centering element having a shaft part 14 and a headpart 16, with the head part having an at least approximately ring-likerecess 20 at its side 18 remote from the sheet metal part 10 with thering recess merging at the radially inner side into a cylindricalsection 21 of the head part 16 which in turn merges into the shaft part14 and a tubular rivet section 22 which surrounds the shaft part 14 inthe region of the head part 16, i.e. directly beneath the head part 16.The ring recess 20 is arranged within a ring-like contact surface 24disposed radially outside of the ring recess, or radially outside of acontact surface consisting of circular ring segments 24′, and merges atthe radially outer side via an at least approximately conical wall 23into the contact surface 24 or 24′. The conical wall 23 canadvantageously have an included cone angle as shown of approximately 33°relative to a horizontal plane, with this angle being able to beselected straightforwardly in the range from 20° to 45° and these valuesshould also not be considered restrictive.

Radially within the conical wall the ring recess 20 has in thisembodiment a curved ring-like base surface 26 at least in half-crosssection which merges into the radially outer surface 28 of the cylindersection 21. In this example the base surface 26, which is curved inradial half cross section, includes a flat section 28 which standssubstantially perpendicular to the central longitudinal axis 30 of theelement 12. It would however be conceivable to omit the flat basesurface or to expand the radial width of the flat section 28 so that itmerges directly or via a relatively small radius into the conical wall23 and/or into the cylindrical section 21 above the rivet section 22(not shown). The base surface could also be realized differently, i.e.by a relative sharp transition of the conical wall into the cylindricalsection 21 above the rivet section 22 (with the term “above” beingunderstood for the shown orientation of the element 12 and not as ageometrical definition).

At least one local recess 32 and preferably a plurality of in particularuniformly distributed local recesses 32 is or are provided in theconical wall 23 of the ring recess 20 and/or in the optionally providedbase surface 26 of the ring recess 20.

The or each local recess 32 has an elongate rounded shape, with thetransition from the side walls of each local recess merging in thisembodiment via a sharp edge into the surface of the ring recess 20.These transitions could however also be made rounded.

The or each local recess 32 is essentially arranged in a radial planeand is made so long in this embodiment that it extends into thering-like contact surface, whereby the ring-like contact surface 24 issubdivided into circular ring segments 24′, as can in particular berecognized at the points 24′, 32′, 24 at the left hand side of FIG. 1B.The designation “ring-like contact surface” is thus to be understood insuch a way that it also covers a contact surface composed of circularring segments which is interrupted by such local recesses. It is,however, also possible to make the local recesses shorter so that theydo not reach the contact surface 24 and do not subdivide it.

In precisely the same way as the local recesses subdivide the ring-likecontact surface 24 in this example they also subdivide the base surface26 of the ring recess 23. When this base surface 26 is termed ring-likethen this is to be understood in such a way that this also includes abase surface which is interrupted by one local recess or by a pluralityof local recesses.

In this example six uniformly distributed local recesses are provided.However, a different number of recesses can also be straightforwardlyprovided—from one local recess up to twelve local recesses would becompletely conceivable—and a larger number could also be considered,above all if they are made smaller or narrower and less deep.

As can be seen from the drawing, in particular from FIG. 1B the free end34 of the wall of the tubular rivet section is rounded when seen in aradial section plane (as shown at the right hand side in FIG. 1B) bothat the radially outer side and also at the radially inner side and has,for example, a semicircular shape or a shape resembling an arrow tip,whereby a ring apex at the lower end of the rivet section arisesprecisely at the position designated by 34.

In the embodiment of FIGS. 1A-1C and 2A, 2B, the shaft part 14 is formedas a solid or tubular centering part. Instead of forming the element asa pure centering element it can also be formed as a centering andattachment element in accordance with FIGS. 3A to 3C and FIGS. 4A and 4Brespectively.

In the description of the embodiment of FIGS. 3A to 3C and FIGS. 4A and4B features which have the same shape and/or the same function as in theembodiment of FIGS. 1A to 1C and FIGS. 2A and 2B are provided with thesame reference numerals and it will be understood that the samedescription also applies for the corresponding features or functionunless something is stated to the contrary. It also applies inversely,i.e. the description of FIGS. 3A to 3C and of FIGS. 4A and 4B alsoapplies to the embodiment of FIGS. 1A to 1C and FIGS. 2A and 2B unlesssomething is stated to the contrary. For the sake of brevity thedescription will thus not be un-necessarily repeated. In the embodimentof FIGS. 3A to 3C and FIGS. 4A and 4B the shaft part 14 is provided witha thread 14′.

The thread 14′ has a thread run-out 14″ adjacent the region of the freeend of the tubular rivet section and the thread run-out merges into acylindrical section 40 with a diameter which is of the same size as orlarger than the outer diameter of the thread. This cylindrical section40, which forms the actual centering section, essentially first comes tolight when the element 12 is attached to the sheet metal part 10, asshown in FIG. 4B. In the embodiment of FIGS. 1A to 1C and 2A, 2B eitherthe entire shaft part 14 beneath the turned over rivet section, i.e. therivet bead 42, form the centering section 40 or however only a partdirectly beneath the rivet bead 42, with it being possible for theremaining part to be stepped, i.e. provided with a smaller diameter forpre-centering.

Various possibilities exist for modifying the elements in accordancewith FIGS. 1A to 1C and 3A to 3C. For example, the head part can have afunctional section at the side opposite to the shaft part, for examplein the form of an outer thread, an inner thread, a further shaft partwith a clip mount or a guide part. As a further alternative the shaftpart 14 could be made longer and either serve as a guide for a pin or ashaft or be provided with an internal thread.

The method for the attachment of the element 12 of FIGS. 1A to 1C to asheet metal part will now be described with reference to FIGS. 2A and2B. It is pointed out that the same description also applies for theattachment of the element 12 in accordance with FIGS. 3A to 3C to asheet metal part 10 in accordance with FIGS. 4A and 4B, which is broughtto expression by the use of the same reference numerals. The descriptionof the method in accordance with FIGS. 2A and 2B will thus not berepeated for the FIGS. 4A and 4B.

As shown in FIGS. 2A (4A) the element 12 is inserted into a pre-holedsheet metal part 10 which has been pre-shaped to the region of the hole50 to a raised portion 52 which is at least substantially matched to theshape of the ring recess 23. In this example the raised portion 52 ofthe sheet metal part is flattened off at the top 53 and the hole 50 hasbeen subsequently pierced, whereby the side wall 53 of the hole extendsparallel to the longitudinal axis 30. The pre-given flattening ishowever not essential and the conical raised portion 52 could bestraightforwardly formed without a flattened portion 53. The stamping ofthe hole 50 could also be simultaneously combined with the pressingprocess for the formation of the hole 50, whereby the hole 50 wouldextend conically and would diverge upwardly in FIG. 2A. As a furtheralternative the raised portion can have a steeper conical shape than theconical wall 24 of the ring recess 23.

The attachment of the element to a sheet metal part takes place in amanner known per se with the means of a die button in a press orC-frame. In this arrangement pressure is for example exerted onto thehead part of the element while the sheet metal part is supported on thedie button. By means of the die button (not shown), which has a centralsection or a central bore which receives the shaft part and a ring-likeraised portion surrounding the section or the bore, the sheet metalmaterial around the rivet section 22 is formed into the or each localrecess 32. The rivet section 22 is laid during the formation of therivet bead 42 into the ring recess 54 formed in the lower side of thesheet metal part 10.

For this purpose the ring-like raised portion of the die button ispreferably formed at its free 30 end with a ring edge which merges intoa rounded shaping surface disposed radially outside of the ring edge.The diameter of the ring edge is selected to be somewhat smaller thanthe diameter of the ring apex at the free end of the rivet section 22,whereby the rivet section 22 is deflected radially outwardly during theriveting process by the ring edge and the rounded shaping surface andformed into a rivet bead 42. In this connection the sheet metal materialis so crushed by the forces exerted between the head part 16 of theelement and the die button, by the rivet bead that is forming and by theregion of the die button radially outside of the rivet bead, that thesheet metal material flows into the local recess(es) 32 and there formsraised portions in the sheet metal material which form a toothedinterlock between the element and the sheet metal part 10 providingsecurity against rotation. Through the beading over of the rivet sectionthe sheet metal material is moreover clamped into a radial groove 56formed between the ring recess 20 and the rivet bead 42, which securesthe element in the axial direction in the sheet metal part. The sheetmetal material is moreover firmly pressed against the shaft part 14 ofthe element in the region above the rivet bead 42 by the crushing forces(and the simultaneously occurring dilation of the rivet section) wherebya high hole friction arises which produces a firm positioning of theelement and an increased resistance to rotation.

Moreover, the sheet metal material is placed in compression so that indynamic operation no fatigue cracks are to be feared. This effect can beincreased further when the conical raised portion of the sheet metal ispartly pressed flat, i.e. when the clamping or riveting process is usedin accordance with the initially named EP-A-0 539 793.

The result of the method is thus a component assembly comprising thesheet metal part 10 and the element 12 attached thereto, with the sheetmetal part 10 having a ring-like raised portion 52′ in the region of thering recess 20 which is received in form-fitted manner into the ringrecess 20, with the material of the sheet metal part being disposed inthe or in each local recess 32. Furthermore, a ring recess 60 is presentat the side 58 of the sheet metal part 10 remote from the ring recess 22with the rivet section which has been beaded over into the rivet bead 42being located in the ring recess 60. The side of the rivet bead 42remote from the head part 16 projects at least substantially not beyondthe side 58 of the sheet metal part in the region around the rivet beadand is preferably set back slightly relative to the latter, for exampleby 0.02 mm.

A use of the component assembly of FIG. 4B with a further component 70is shown in FIG. 5. The component has a hole 72.

The inner diameter of the hole 72 is at least substantially identical tothe outer diameter of the shaft part 14 in the region of the rivet bead42, i.e. of the centering section 40, and the component is centered bythis region of the shaft part.

The component 70 is held against the sheet metal part 10 by means of afastener element 74 attached to the shaft part 14 of the element, forexample, on forming the shaft part with an external thread 14′, by a nut74 screwed onto the thread 14′, optionally the intermediary of a washer76. As an alternative to this the shaft part can be formed as a tubularpart with an internal thread (not shown) and the component 70 can thenbe secured by a screw screwed into the internal thread.

For the sake of completeness it should be pointed out that the elementsin accordance with the invention need not necessarily satisfy thecentering function, but rather it could have a pure fastening functionand need therefore not necessarily be a centering element or centeringbolt.

In all embodiments all materials can be named as an example for amaterial of the element which achieve the strength values of class 8 inaccordance with the ISO standard or higher in the context of colddeformation, for example a 35B2 alloy. The so formed fastening elementsare also suitable for all commercially available steel materials fordrawing quality sheet metal parts as also for aluminum or its alloys.Also aluminum alloys, in particular those with higher strength can beused for the elements, for example AlMg5. Also elements of higherstrength magnesium alloys such as for example AM50 could be considered.

Referring to FIGS. 6A to 6C an element 12 is shown which can be attachedto a sheet metal part 10 by riveting. The element 12 has the form of acentering element having a shaft part 14 and a head part 16, with thehead part having an at least approximately ring-like recess 20 at itsside 18 remote from the sheet metal part 10 with the ring recess mergingat the radially inner side into a cylindrical section 21 of the headpart 16 which in turn merges into the shaft part 14 and a tubular rivetsection 22 which surrounds the shaft part 14 in the region of the headpart 16, i.e. directly beneath the head part 16. The ring recess 20 isarranged within a ring-like contact surface 24 disposed radially outsideof the ring recess, or radially outside of a contact surface consistingof circular ring segments 24′, and merges at the radially outer side viaan at least approximately conical wall 23 into the contact surface 24 or24′. In the embodiment of FIGS. 6A-6C, the shaft part 14 is formed as atubular centering part 78.

Turning to FIGS. 7A to 7D, which show the use of component assemblieswith further components 70 as is shown e.g. in FIG. 5. However, in theembodiments of FIGS. 7A to 7D the element 12 is provided with afunctional section 80 at the side of the head part 16 opposite to theshaft part 14. FIG. 7A shows a functional section 80 which can be usedas a guide, but can equally be used as a centering part. FIG. 7B shows afunctional section 80 including a clip mount. FIG. 7C shows a functionalsection 80 including an inner thread. FIG. 7D shows a functional section80 including an outer thread.

1. A method for the attachment of a centering element to a sheet metalpart (10) for the formation of a component assembly, said centeringelement (12) having a shaft part (14), a tubular rivet section (22)surrounding said shaft part and a head part (16), said head part havinga cylinder section (21), a side (18) confronting said sheet metal part,a recess (20) at least approximately in the shape of a ring in said sideand an annular sheet metal contact surface (24; 24′) surrounding saidrecess, said recess merging at a radially inner side into said cylindersection (21) of said head part (16) and said cylinder section (21) inturn merging into said shaft part (14) and said cylinder section alsomerging into said tubular rivet section (22) which surrounds said shaftpart (14) in a region of said head part (16) and being disposed withinsaid annular contact surface (24; 24′) and said recess merging at aradially outer side via an at least approximately conical wall (23) intosaid annular contact surface, there being a plurality of local recesses(32) provided in at least one of said conical wall (23) of said recessand in a base surface (26) of the ring shaped recess, and wherein aregion of said shaft part (14) forms a centering section (40) radiallywithin said tubular rivet section (22) adjacent said cylinder section(21), the method comprising the steps of inserting said region of saidshaft part forming a centering section (40) into a pre-formed hole ofsaid sheet metal part (10), forming material of said sheet metal partsurrounding said tubular rivet section (22) into the local recesses (32)by means of a die button having a central recess which receives saidshaft part and a raised portion in the form of a ring which surroundssaid central recess and pressing said rivet section (22) into a ringrecess (20) formed in the underside of the sheet metal part duringformation of a rivet bead (42) from said tubular rivet section (22). 2.A method in accordance with claim 1 including the step of pre-shapingsaid sheet metal part in the region of the hole to form a raised portion(52) which is one of matched at least substantially to the shape of thering recess (20) and has a steeper conical shape than the conicalwall(23).
 3. A method in accordance with claim 1, said ring shapedraised portion of said die button being formed at its free end at leastsubstantially with a ring edge which merges into a rounded shapingsurface disposed radially outside of the ring edge, said ring edgehaving a diameter smaller than a diameter of a ring edge formed at afree end of said tubular rivet section, whereby the rivet section (22)is formed into a rivet bead (42).